Papers by Keyword: Adsorption

Abstract: The effects of interstitial nitrogen atoms on the adsorption of atomic oxygen on fcc Fe (001) surface have been studied using ab initio density functional theory calculations to understand the initial stage of oxidation on nitrogenous austenitic stainless steel. It has been found out that the N atoms can improve the adsorption ability of the O atom at the hollow site on the surface, and thus promote the rapid passivation of nitrogenous austenitic stainless steel. This improvement is possibly because the Coulombic interactions between the O atom and the neighboring Fe and Cr atoms are enhanced due to the electron transfer from the Fe and Cr atoms to the N atoms.

Abstract: Graphene (GR) aerogels with three-dimensional interconnected network were prepared from freeze drying graphene oxide (GO) dispersions for adsorbing organic reagents. Microstructures of GR aerogels were observed by field-emission scanning electron microscopy, and the components were analyzed by X-ray photoelectron spectroscopy and X-ray diffraction. Their adsorption abilities and recycling performances for organic reagents were investigated in detail. The results showed that the adsorption capacity of GR aerogels was dependent on the concentration of GO dispersion. For example, the adsorption capacity of ethanol increased from 7.04 to 32 g/g when the GO concentration changed from 5 to 10 mg/ml. The GR aerogels also exhibited good adsorption performance for other organic reagents, reaching 44.78, 93.41 and 56.56 g/g for cyclohexane, acetone and methanol, respectively. Moreover, the 7GR had good cyclic adsorption capacity for cyclohexane, acetone and methanol, and the relative standard deviation was 3.7%, 4.3%, 3%, respectively.

Abstract: Palm oil mill efluent (POME) is the major industrial waste water in Malaysia and Indonesia. The processing of (POME) before discharge is a major challenge to researchers. In this study, the adsorption experiment of zinc ion from (POME) produced from the processed palm oil as primary treatment has been investigated using coconut shell and cow bone activated carbon. Experiments were conducted at a fixed initial concentration, contact time, shaking speed and at different adsorbent dosage to obtain optimum condition for the uptake of zinc ion from POME. The coconut shell carbon exhibited better removal efficiency than the cow bone powder. The results obtained at fixed condition of pH 7, contact time of 105 minutes, shaking speed of 150 rpm showed more than 90% uptake for both adsorbents. The result of the adsorption study was further analyzed using Langmuir and BET model to determine the experimental isotherm. The result showed that equilibrium data fitted better with BET model for coconut shell carbon and better with Langmuir model for cow bone powder. The result of the adsorption experiments showed that heavy metal of zinc can be sufficiently reduced on both coconut shell carbon and the cow bone powder. The morphology of both adsorbents was observed using the scanning electron microscope (SEM), the pore sizes of the adsorbents supported the uptake of zinc ion from the raw POME.

Abstract: Natural clay (NC) and its surface modified with manganese oxide (MnO-NC) was assessed for removal of Cd (II) ion by batch adsorptive process. The surface modification of NC was chemically prepared with manganese chloride in basic solution by simple procedure, resulting in larger surface area than raw material by about 10-times. FT-IR spectra and SEM photograph showed the unique characteristic of MnO-NC after chemically surface modification with MnO₂ particles successfully set down onto the NC surface. Under optimum conditions as a function of solution pH of 6.0, adsorbent dose of 5 g/L, contact time of 15 min and initial cadmium concentration of 100 mg/L, the adsorption capacity reach to 30.6 mg/g. By comparing with NC, MnO-NC provides higher adsorptive capability than the one by about 30-times. Based on isotherm estimation, the Langmuir adsorption isotherm showed more suitable for both adsorbents with the best correlation coefficient (r²>0.99) than the Freundlich isotherm. The adsorptive kinetics of Cd (II) onto NC and MnO-NC followed the pseudo-second-order.

Abstract: An autoclaved aerated concrete (ACC) was chemically modified with manganese oxide (MnO-ACC) for investigate as a high effective adsorbent for removal of lead ions from aqueous solution. The precipitation reaction of manganese oxide was easily done under a high basic solution, resulting manganese oxide in a micron scale occupy on the surface of ACC. The maximum removal efficiency of lead ions using MnO-ACC was obtained under a function of pH 7, adsorbent dosage of 5 g/L, equilibrium time of 15 min. The experimental data were analyzed by commonly adsorption models. The Langmuir adsorption isotherm model is more suitable with a good correlation coefficient of R²=0.99 than the Freundlich model. The maximum monolayer adsorption capacity (q_max) of MnO-ACC was found to be 43.22 mg g⁻¹ in which higher adsorptive capable than unmodified ACC by about 10 times. Based on kinetics study, the adsorption of lead ions onto MnO-ACC followed a pseudo second-order model with a good correlation coefficient of R²=0.99.

Abstract: The article gives considerations to issues dealing with systems for separation and purification of gas mixtures containing methane. A method of pressure swing adsorption is suggested for biogas purification. The present results show the use of natural zeolite (Izhberdinskoye field, Orenburg region) to improve biogas quality by adsorption of water vapor, hydrogen sulphide and carbon dioxide.

Abstract: Bentonite has been purified by suspension method and sodiumed with sodium carbonate, and then modified with polyaniline. Finally, characterized by the polarizing microscope, the X-ray diffractometer(XRD) and Fourier infrared spectrometer (FT-IR), in order to determine the optimal preparation technology of polyaniline/bentonite. And the optimal preparation of PAn/MMT is used to research the adsorption dynamics analysis on phenol. The result shows that the sodium ion enters into the bentonite interlayer through ion exchange; When the dosage of bentonite is 5 g, the dosage of FeCl₃·6H₂O is 2.7 g, the dosage of aniline is 46.5 g, and the dosage of DBSA is 3.26 g, its layer spacing of modified bentonite is 2.823nm, increaseing 1.600nm than the first, so the hydrophobicity and separation effects of the modified bentonite get greatly improvement. And the dosage of PAn/MMT is 0.1 g and the initial concentration of phenol、P-nitrophenol、o-cresol is 10 mg/L, their adsorption rates reach to 51.50%, 80.56%, 62.93%, more high than the sodium bentonite under the same conditinns. It indicates that the modified bentonite is more suitable for the adsorption of benzene homologs.

Abstract: The adsorption properties of water molecules on cellulose and cellulose nanocrystals (CNCs), isolated from defatted rice bran (DRB) by 55% sulfuric acid hydrolysis under sonication were investigated. The powdered samples of cellulose and CNCs were analysed by using near infrared spectroscopy (NIR) and gravimetry at 38% and 55% humidities. Small amounts of samples were dried under vacuum at 120°C and the NIR spectra of the dry samples and their spectra during the adsorption water molecules were measured by using an NIR spectrometer equipped with a transflectance accessory and a DTGS detector. The quantitative adsorption of water molecules by the samples was determined by gravimetry. Second and fourth derivative profiles of the NIR spectra were used in understanding the chemistry of adsorption of water molecules and the adsorption processes by the samples. The results show that the adsorption of water molecules by the cellulose samples gives rise to three prominent peaks that can be related to the water molecules engaged in hydrogen bonding with C2, C3 and C6-OH groups on the glucose units of the cellulose polymers. Furthermore, the cellulose nanocrystals adsorb twice as much of water as the cellulose polymer. It is also clear from the results that C2 and C3-OH groups in the glucose units adsorb water molecules at a faster rate than the C6-OH group and responsible for nearly 50% of the water adsorption.

Abstract: Research about comparison of chitosan modified by swelling and formaldehyde crosslinked in adsorption of metal ion Cu (II) on variation of pH solution and concentration of chitosan has been done. The purpose of this research are to: 1) Determine the degree of deacetylation of chitosan and modified chitosan by swelling and formaldehyde crosslinked. 2) Determine the adsorption capacity of chitosan modified by swelling and formaldehyde crosslinked in adsorption of Cu (II) metal ion. The result of the research showed that: 1) The degree of deacetylation on optimum conditions of each chitosan was 70,3% for technical chitosan; 89,7% for modified chitosan by swelling and 82,5% for chitosan formaldehyde crosslinked. 2) The adsorption capacity in the optimum condition of chitosan modified by swelling and crosslink for the adsorption metal ion Cu (II) were 77,42%, and 75,16%.

Abstract: Based on the selective adsorption property of the imidazolium-type hyperbranched polymeric ionic liquid (hb-PIm⁺PF₆^-) towards anionic dyes, it was incorporated into poly(vinylidene fluoride) (PVDF) matrix to modify PVDF film. The composite hb-PIm⁺PF₆^-/PVDF films were prepared via non-solvent-induced phase inversion method. The obtained composite films were characterized by attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy, and contact angle goniometry. Using bromophenol blue (BPB, an acidic dye) as the model molecule, the dynamic and static adsorption properties of the hb-PIm⁺PF₆^-/PVDF films were investigated, respectively. It is significant that the hb-PIm⁺PF₆^-/PVDF composite films could efficiently remove BPB from water under dynamic condition.